Sample code in test.php to fetch an access token for scope firebase messaging. For this sample to work you need a Google service account configuration file and name the file serviceaccount.json. The fields used from the service account file are: token_uri, client_email, private_key_id, private_key.

Implement the interface \GSAToken\JWTFactory to use your own methods of creating a signed JWT. Note! It must support RS256 signed JWT as this is what Google expects.

interface JWTFactory
{
	// Return a string with the signed JWT token
	public function create($header, $claims, $secretkey);
}

class JWTCreator implements \GSAToken\JWTFactory
{
    public function create($header, $claims, $secretkey)
    {
        return createJWT($header, $claims, $secretkey);
    }
}

Implement the interface \GSAToken\HttpClient to use your own http client to perform the request. An included implementation in class DefaultHttpClient is used by default. It uses curl if available, otherwise file_get_contents.

interface HttpClient 
{
	// Perform a http request
	// Should return an array with these fields
	// array("body" => $response, "httpcode" => $httpcode, "headers" => $responseheaders, "error" => $error);
	public function request($method, $url, $headers, $postdata);
}

Implement the interface \GSAToken\TokenCache to cache the access token. The included FileTokenCache shows an implementation where the token is encrypted and stored in a file on disk. For example, you may want to store it in a database.

interface TokenCache
{
	public function isValid($now);
	public function getToken();
	public function load();
	public function save($token);
}

The implementation has been tested in php 5.6 and 8.2. Two shell scripts are included to run php cli via docker. This way no need to install php locally. You need docker installed and then pull the php images referenced in the files or you may change to any version you want. Then run:

$ ./php56-cli.sh test.php